This application is based on and incorporates herein by reference Japanese Patent Applications No. 2002-122161 filed on Apr. 24, 2002 and No. 2003-81175 filed on Mar. 24, 2003.
The present invention relates to an engine control apparatus for detecting a crankshaft angle position with a rotation signal of an engine.
The present invention relates to an engine control apparatus for detecting a crankshaft angle position with the rotation signal of an engine.
A control apparatus for a vehicular engine detects a crankshaft angle position by detecting the turns of the crankshaft of an engine by means of a rotation angle sensor and by introducing the rotation signal into a microcomputer. Moreover, the rotation signal is provided with a missing tooth reference position. Various methods for detecting the missing tooth are proposed.
In U.S. Pat. No. 5,264,844 (JP-A-5-66105), for example, the missing tooth detection is executed by a hardware circuit, which is provided with a rotation transmitter, an up-down counter 11 And an f/K frequency divider. In U.S. Pat. No. 6,341,253 (JP-A-2001-214794), the position of the crankshaft angle is detected by a microcomputer control to make an ignition control at a starting time when a premature ignition control is made for improving the startability. In U.S. Pat. No. 4,715,009 (JP-B-7-65905), a missing tooth is detected by measuring pulse periods of three successive pulses. In JP-B-7-18379, there are provided two larger and smaller missing tooth determination values, the larger of which is used at an engine starting time to detect the missing tooth thereby to prevent the erroneous missing tooth detection, as might otherwise be caused by the rotational fluctuation at the starting time.
According to the missing tooth detection by hardware, for example, the processing load on the microcomputer is reduced, but the missing tooth may be erroneously detected at low speed regions when the engine speed is unstable. According to the missing tooth detection by software (or microcomputer), on the other hand, a flexible response to the missing tooth detection can be made, but the processing load increases.
The invention has an object to provide an engine control apparatus, which can execute detection of a reference position properly immediately after an engine start or at a subsequent ordinary running time.
According to the present invention, an engine control apparatus comprises a rotation signal generating circuit, a signal processing circuit and a microcomputer. The rotation signal generating circuit generates a rotation signal composed of a train of pulses at each interval of a predetermined angle corresponding to the turns of the crankshaft of an engine and having a reference position of a different pulse width intermediate of the pulse train. The signal processing circuit measures the pulse interval by inputting the rotation signal and detects the reference position on the basis of the pulse interval, to output a reference position signal corresponding to the reference position. The microcomputer inputs the rotation signal and the reference position signal, to detect a crankshaft angle position from the rotation signal and the reference position signal thereby to execute various engine controls.
Especially, the microcomputer starts an interrupt at each effective edge of the rotation signal and executes the measurement of the pulse interval by the interrupt and the detection of the reference position on the basis of the pulse interval. It detects, by making the detection result of the reference position by the interrupt effective at the beginning of the start of the engine, the crankshaft angle position on the basis of the detection result. After the engine start and when it is determined that the signal processing circuit is normally operating, the microcomputer detects the crankshaft angle position with the reference position signal, by making the reference position signal from the signal processing circuit effective in place of the result of the reference position by the interrupt.
At the beginning of the engine start, moreover, the crankshaft angle position (or the rotational position of the engine) is detected from the detection result of the reference position by the software. Even at the time immediately after the engine start when the turns of the crankshaft are unstable, therefore, it is possible to detect the reference position properly and the crankshaft angle position precisely. On condition of the determination that the signal processing circuit is normally operating after the engine start, moreover, the reference position detecting means is switched to the hardware. After the engine start was completed, therefore, the detection of the reference position by the interrupt is not essential so that the processing load on the microcomputer can be reduced. As a result, the detection of the reference position can be properly executed from the engine start to the ordinary run.
Alternatively, the microcomputer detects the crankshaft angle position with a reference position signal from the signal processing circuit at an ordinary run of the engine by making the reference position signal effective. Moreover, the microcomputer starts an interrupt at each effective edge of the rotation signal when the speed of the engine drops to a predetermined threshold value or lower. The microcomputer executes the measurement of the pulse interval by the interrupt and the detection of the reference position on the basis of the pulse interval, and detects, by making the detection result of the reference position by the interrupt effective, the crankshaft angle position on the basis of the detection result.
In this case, when the engine speed drops, the turns of the crankshaft may become unstable when the engine speed drops, and the reference position detection by the microcomputer (or software) is executed temporarily only when speed drops. Therefore, the detection of the reference position by the interrupt can be executed necessarily to the minimum thereby to reduce the processing load on the microcomputer. Moreover, the detection of the reference position can be properly executed throughout all the drive ranges.